A nurse is caring for a client who was prescribed metformin 6 months ago. Which of the following findings indicates a positive response to the medication?

Rationale: A. The client's frequency of incontinence has decreased: Incontinence is not a direct measure of blood glucose control or the effectiveness of metformin. Changes in urinary frequency may be influenced by other conditions, such as urinary tract infections or prostate issues, and do not indicate the medication’s success. B. The client's iron level has increased: Metformin does not affect iron metabolism. An increase in iron levels would be unrelated to metformin therapy and could reflect dietary changes, supplementation, or other underlying conditions. C. The client's high-density lipoprotein level has increased: While metformin may have mild beneficial effects on lipid profiles, its primary purpose is to improve glycemic control. Changes in HDL are not the main indicator of therapeutic success for this medication. D. The client's HbA1c has decreased: HbA1c reflects average blood glucose levels over the past 2–3 months. A decrease indicates improved glycemic control, which is the primary goal of metformin therapy. Monitoring HbA1c is the most reliable measure to evaluate the effectiveness of the medication.